回复：10多年前我验血没抗体也没乙肝病毒 故注射过预防针

How long does protection from Hepatitis B vaccine last?

Studies indicate that immunologic memory remains intact for at least 20 years among healthy vaccinated individuals who initiated Hepatitis B vaccination >6 months of age. The vaccine confers long-term protection against clinical illness and chronic Hepatitis B virus infection. Cellular immunity appears to persist even though antibody levels might become low or decline below detectable levels.

Among vaccinated cohorts who initiated Hepatitis B vaccination at birth, long-term follow-up studies are ongoing to determine the duration of vaccine-induced immunity.

more info:http://www.cdc.gov/hepatitis/HBV/HBVfaq.htm#overview
问:我儿中学也统一注射过预防针，是不是也该打针了。
答:完成了三针(three doses)的注射,就不需再打了.